As pointed out in application Ser. No. 460,620, the use of magnetic suspension vehicles has become increasingly significant in recent years for a variety of reasons. In conventional rail systems of the type primarily used heretofore for the transportation of passengers and freight, the vehicle speed was limited by the frictional interaction of the supporting track structure and the vehicle.
In such systems, the vehicle is carried by wheels or the like which roll upon rails of the track and are driven by electric motors or other means such that the wheels roll upon substantially continuous supporting surfaces. The wheels bear against these surfaces with rolling friction under the distributed weight of the vehicle and the load. The rolling friction increases with loading and becomes increasingly significant as vehicle speed increases.
This is not only a consequence of power loss but also a consequence of the fact that friction limits loading speed and operating life of the frictionally interengaging parts as well as the parts supporting the rolling members.
Considerable attention has been directed in recent years toward reducing the considerable friction forces which have hitherto limited high speed rail travel as described above.
In general, two approaches have been taken towards limiting frictional engagement of the vehicle with a supporting track. One such approach involves the use of a fluid cushion (for instance an air cushion) between the vehicle and the track, while the other suspends the vehicle electromagnetically from a track or other substantially continuous support. For this purpose the vehicle is provided with an electromagnetic arrangement whose cores are juxtaposed with an armature rail extending along and fixed to the track too maintain a suspension air gap between the vehicle and the track which is spanned by a magnetic field.
A typical construction of this type makes use of a T-section track having a pair of armature rails disposed along the underside of the cross bar of the T and juxtaposed with respective rows of electromagnets on the aprons of the vehicle underhanging the rails.
In another construction, the T-shaped track is provided with armature rails along the upper surfaces of the cross bar and the electromagnetic cores are juxtaposed with these rails.
Still another arrangement provides a channel configuration for the track such that the latter is generally of U-profile and the armature rails are disposed along the shanks of the U. The vehicle may have oppositely laterally extending formations carrying rows of electromagnets.
In the aforementioned applications various systems have been discovered which overcome disadvantages of both the T-section track and the channel-shaped track and which enable transfer of the vehicle from one track portion to another, i.e., to permit switching or cross-over of the vehicle from a main track to a spur track and vice versa without necessitating swinging track portions which are expensive to construct and difficult to control.
In the system described in application Ser. No. 460,620 (extending principles set forth in Ser. No. 324,135 (U.S. Pat. No. 3,842,747)), a row of main electromagnets is provided along each side of the vehicle for cooperation with main armature rails and, for each main row of electromagnets, there is provided a row of auxiliary electromagnets which cooperate with auxiliary armature rails only at switch-over portions along the track where the corresponding main electromagnet temporarily passes away from the respective main armature rail or the latter must be interrupted to permit crossover. In the system described in application Ser. No. 362,012 (U.S. Pat. No. 3,851,594) at least one subrow of each longitudinal electromagnetic arrangement or main row is in a state of magnetic interaction with an armature rail at all times during vehicle travel over the track network, i.e., as the vehicle negotiates ordinary lengths of track or at junctions, cross-overs and branching regions.
The system of application Ser. No. 460,620 avoids magnetic shock and magnetic interference by providing both subrows of each magnetic arrangement (main row) and the associated armature rails in vertically offset arrangement so that each subrow of electromagnets and the associated armature rail on one side of the vehicle forms a set which is located at a different level than the other set of the same row, the lower sets of the two magnet arrangements being either the two outermost sets or the two innermost sets with respect to the vertical median plane or longitudinal axis of the vehicle.
Generally speaking the above-described system provides separate energizing sources for the main electromagnet and the auxiliary electromagnet so that they can be appropriately turned off as the vehicle passes through a spur, switch-over or curve of the track.
For example, where the auxiliary electromagnets lie relatively inwardly of the main electromagnets, the main armature rails will lie outwardly of the auxiliary armature rails and, assuming a spur to the right from a main track, the left hand main armature rail will extend continuously along the main track, the right hand main armature rail will extend continuously along the spur, the left hand main armature rail of the main track and will continue beyond the spur. Since a vehicle branching to the spur from the main track will have its main left electromagnet withdrawn from the corresponding main armature rail, its auxiliary left electromagnet must be energized to cooperate with an auxiliary armature rail during the transition to the spur and, should the vehicle travel pass the spur on the main track, its right hand electromagnet will leave its rail so that the vehicle must be supported at the right hand side by cooperation of its auxiliary right hand electromagnet with the armature rail. Consequently, the main electromagnets may have to be de-energized and re-energized at different locations at the junctions and the corresponding auxiliary electromagnets energized or de-energized to maintain the appropriate suspending and guiding forces at both vehicle sides.
In switch constructions in which the auxiliary armature rails are flanked by the main armature rails, it is necessary on the passage of the vehicle across a switch that the main electromagnet along the outer limb be de-energized and the corresponding auxiliary electromagnet switched on alternately while along the inner limb of the curve, only the main electromagnets need be energized continuously.
For convenience, in a curved track configuration, the outer limb will correspond to the outer-curved portions or the outside of a curved track while the inner limb will mean the inside of a curved track. The vehicle side sweeping the outer limb will be termed the outer-curved vehicle side while the inner limb is swept by the inner-curved vehicle side.
In systems where a common energization source is provided for both the auxiliary and main electromagnets on each side, there is the difficulty that from time to time the vehicle direction becomes ill-defined; hence such systems are undesirable since it is not possible to independently switch off the main and auxiliary electromagnets on each side.
It has been proposed to provide separate energization of the main electromagnets and auxiliary electromagnets on each vehicle side. This system has been found to be disadvantageous since it is necessary to provide separate regulating means and additional control circuits for each group of control coils. This not only increases the expense of the transportation system as a whole but, since much of the regulatory circuitry must be carried on the load-carrying vehicle, decreases the payload and creates space problems on the vehicle itself.